Crash prevention Australian engineers have developed a new laser air speed sensor which could help to prevent aircraft crashes.

Existing sensors - known as Pitot tubes - have been considered as possible causes for several fatal aircraft accidents.

In June 2009, the Air France Airbus A320 went down in the Atlantic Ocean off the coast of Brazil, while on a flight from Rio de Janeiro to Paris, claiming 228 lives.

The official air crash investigation concluded the likely cause was a build up of ice in the Pitot tubes affecting the readings reaching the autopilot.

Dr Sean O'Byrne and Dr Sven Wittig from the University of New South Wales were developing hypersonic air speed sensors to monitor air flow in scramjet engines, as part of Wittig's PhD research, when the Air France crash occurred.

Doing it better

"Pitot tubes are simple, cheap and reliable, but can give false readings if obstructed by dirt build-up, birds, insects or ice in bad weather," says O'Byrne.

"You then need to rely on backups, like GPS, which may not do the job during storms."

The new device calculates airspeed using lasers based on those found in a high-end computer mouse. A sensor detects the Doppler shift of photons in the laser beam as they are absorbed by oxygen molecules in the air.

"Because we're only using laser light, there are no physical components poking out in the airflow," says O'Byrne.

"Instead they're located behind a window built into a recess in the aircraft wing or fuselage, where the temperature can be controlled."

Using the Defence Science and Technology Organisation's high-speed wind tunnel, O'Byrne and Wittig carried out proof-of-concept testing of the new sensor.

"The next step is to scale down the technology into an aircraft ready design and conduct flight tests," says O'Byrne.

While not designed to replace Pitot tubes, O'Byrne says they would be a low-cost measure to augment the tubes, giving pilots more confidence in their readings and helping guard against fatal crashes.